1. The Field of the Invention
The present invention relates to rendering of objects on a display; and more specifically, to the display of such objects such that a pixel of the display may represent information from multiple sample points of the object for improved resolution.
2. Background and Related Art
Computing technology has transformed the way we work and play. Computing systems now take a wide variety of forms including desktop computers, laptop computers, tablet PCs, Personal Digital Assistants (PDAs), and the like. Even household devices (such as refrigerators, ovens, sewing machines, security systems, and the like) have varying levels of processing capability and thus may be considered computing systems. As time moves forward, processing capability may be incorporated into a number of devices that traditionally did not have processing capability. Accordingly, the diversity of computing systems may likely increase.
Almost all computing systems that interface with human beings use a display to convey information using the user's sense of sight. In many cases, the appeal of the display is considered an important attribute of the computing system. Color displays in particular are quite appealing to users.
Displays are typically composed of picture elements called “pixels”. For color displays, each pixel includes a number of pixel sub-components, each capable of emitting a particular color. For example, most Liquid Crystal Displays (LCDs) have pixels that have an RGB color configuration. In other words, each pixel includes a red pixel sub-component capable of emitting only red light at varying intensities, a green pixel-subcomponent capable of emitting only green light at varying intensities, and a blue pixel sub-component capable of emitting only blue light at varying intensities.
When the display is viewed at a normal viewing distance, the light emitted from the pixel sub-components of a given pixel appears additive to the human viewer. If each pixel sub-component for a pixel has minimum intensity, the pixel appears black. If each pixel sub-component for a pixel has maximum intensity, the pixel appears white. By varying the emission intensities of the pixel sub-components, the pixel may be perceived as having any one of potentially even millions of possible colors.
Liquid Crystal Displays (LCDs) are gaining favor and thus will now be described in further detail. FIG. 1A illustrates a known LCD screen 100 comprising a plurality of rows (R1-R12) and columns (C1-C16). Each row/column intersection forms a square which represents one pixel. FIG. 1B illustrates the upper left hand portion of the known display 100 in greater detail.
Note in FIG. 1B how each pixel element, e.g., the (R2, C1) pixel element, comprises three distinct sub-elements or sub-components, a red sub-component 106, a green sub-component 107 and a blue sub-component 108. Each known pixel sub-component 106, 107, 108 is one third (or approximately one third) the width of a pixel while being equal (or approximately equal) in height to the height of a pixel. Thus, when combined, the three ⅓ width pixel sub-components 106, 107, 108 form a single pixel element.
As illustrated in FIG. 1A, one known arrangement of RGB pixel sub-components 106, 107, 108 form what appear on close inspection to be vertical color stripes down the display 100. Accordingly, the arrangement of one third width color sub-components 106, 107, 108, in the known manner illustrated in FIGS. 1A and 1B, is sometimes called “vertical striping”.
Another arrangement of RGB pixel sub-components form horizontal striping as illustrated in the display 200 in FIG. 2. The display 200 also comprises a plurality of rows (r1-r12) and columns (c1-c16). Each row/column intersection also forms a square which represents one pixel. However, in this horizontal striping configuration, each pixel sub-component for a corresponding pixel is one third (or approximately one third) the height of a pixel while being equal (or approximately equal) in width to the width of a pixel. While only 12 rows and 16 columns of pixels are shown in FIGS. 1A, 1B and 2 for purposes of illustration, most LCD displays will include many more rows and many more columns of pixels.
Traditionally, a pixel represents one distinct sample point for an object being displayed. The color for a pixel is determined by sampling the color of the object at a single point. The corresponding pixel sub-components then emit the appropriate intensities to give the overall pixel its appropriate sampled color. As expected, the resolution of the displayed object corresponds one-to-one to the pixel resolution.
In some cases, this resolution will be sufficient. In many cases, however, it is desirable for the image resolution not to be restricted by the pixel resolution. For example, small objects such as text or other characters may have features that are smaller than a single pixel. One technology that improves image resolution of such objects beyond the pixel resolution involves sampling from different portions of the image for each pixel sub-component, even for pixel sub-components belonging to the same pixel. Each pixel sub-component may represent information derived from multiple im age sample points. This type of sampling will be referred to as “pixel sub-component based sampling” regardless of whether the pixel sub-component represents information from one sample point or more than one sample points.
Using pixel sub-component based sampling, each pixel sub-component represents information from different portions of the object being rendered. Therefore, resolution is improved in the direction opposite the striping direction. For example, in LCD displays that use vertical striping, resolution is improved in the horizontal direction.
In vertically striped displays using pixel sub-component based sampling, objects having spatial frequency dominance in the horizontal direction are represented particularly well. Horizontal “spatial frequency dominance” when attributed to an object means that the object tends to have more vertically-oriented components than horizontally-oriented components. Vertical “spatial frequency dominance” when attributed to an object means that the object tends to have more horizontally-oriented components than vertically-oriented components.
Most Latin-based characters have varying degrees of horizontal spatial frequency dominance. For example, the capital letter “I” and the number “1” and the lowercase letter “m” are dominated almost entirely by vertical components. Other Latin-based characters have some horizontal components but are still dominated by vertical components such as, for example, the capital letters “H” or “A”. However, not all Latin-based characters have horizontal spatial frequency dominance. A few have vertical spatial frequency dominance. For example, the dash or subtraction “−” symbol and the number sign “#” symbol are dominated by horizontal components. Accordingly, conventional pixel sub-component based sampling renders many Latin-based characters quite well when rendered on a vertically striped display.
Although Latin-based characters have predominantly horizontal spatial frequency dominance, many alphabets throughout the world have different degrees of horizontal and vertical spatial frequency dominance. For example, Chinese-based pictographs (i.e., pictographs of Chinese origin such as Kanji and other East Asian characters) more often have vertical spatial frequency dominance (or at least tend to have less horizontal spatial frequency dominance) in that they tend to have more horizontally-oriented strokes than do Latin-based characters. Accordingly, conventional sub-component based sampling results in better quality rendering on a vertically-striped display for objects such as Latin characters tending more towards horizontal spatial frequency dominance than it does for objects such as Chinese based pictographs having less horizontal spatial frequency dominance or even vertical spatial frequency dominance.
Therefore, what would be advantageous are mechanisms in which sub-component based sampling may be used to better render objects having a spatial frequency dominance that is parallel to the striping direction of the display.